Ultrathin Carbon Nanotubes for Efficient Energy Storage: a First-Principles Study

On the basis of first-principles density functional calculations, the present study sheds theoretical insight on ultrathin carbon nanotube (UCNT) and hydrogenated ultrathin carbon nanotube (HUCNT) for use as potential materials not only for Li-ion battery anode but also for high-capacity hydrogen storage. The highest Li storage capacities in UCNT and HUCNT can be of LiC₄ and LiC₄H₂, respectively, which are higher than that in graphite and LiC₆. Binding between Li (Ca) atoms and these materials are found to be enhanced considerably. Each Li (Ca) atom may bind multi-hydrogen molecules, and the adsorption energies are ideally suited for storing hydrogen under ambient conditions, and the predicted weight percentage of molecular hydrogen are in the range of 6.4–12 wt% exceeding the target set by the United States Department of Energy.